TMS320F28335: 仿真器连接失败

我只用电源给DSP供电，并提供30M有源晶振。当连接JTAG时（仿真器XDS100V3，ccs8.0版本），总是提示：

Error connecting to the target:
(Error -1155 @ 0x0)
Device may be operating in low-power mode. The debugger has forced the device to wake up. Choose 'OK' to attempt to complete the debug connection.
(Emulation package 7.0.188.0)

我确认过很多次，电源供电正常。